The present invention relates to a composite container including at least one tubular fibrous body wall, and a high barrier inner liner member covering the inner surface of said body wall, which composite container is adapted for holding liquids, corrosive products, and products which require storage at non-atmospheric conditions. A high barrier liner is necessary if the composite container in which the liner member is used is to hold a pressured product, such as carbonated liquid, a vacuumed product, such as nuts or potato chips, or products flushed with an inert gas. It is desirable that the liner contain at least one layer of aluminum since aluminum is one of the most cost-effective means for achieving oxygen and water vapor resistance.
The various liner constructions presently employed in composite containers adapted for holding liquids, corrosive materials and non-atmospheric pressurized products possess certain serious drawbacks. For example, in the prior "Anaconda fold" construction--as taught by the Krause U.S. Pat. No. 3,156,401--an edge folding technique for helically wound layers is disclosed which possesses the drawback that is produces a comparatively thick step in the body wall thickness. Even with tough, thin liner components, the step is relatively thick since it contains three layers of liner. Secondly, if a stress is imposed across the liner heat seal, such as by the body resisting internal pressure, the seal is pulled in a peel mode. A heat seal stressed in peel has a stress concentration along the edge of the seal and is far weaker than if the seal were stressed in shear. Thirdly, owing to the round shape of the rolled edge of the fold, there is too often a channel under the seal which cannot be properly sealed off by the end compound in the seam where the liner heat seal meets the metal end.
In the "free foil" liner disclosed in the Wannamaker et al U.S. Pat. No. 3,428,239 and Ahlemeyer U.S. Pat. No. 3,520,463, for example, a paperless film-foil laminate is heat sealed to form an overlapped seam. A problem with this construction for a container which is to hold liquid beverages is that the contained product is free to attack the bare foil edge. Even if the product is not spoiled by the dissolved metal, the seam will be weakened and will open, whereby the can will leak.
In the lapped liner heat seal type of seam construction shown in the Krause U.S. Pat. No. 3,288,341, a tape member is provided over the lapped liner heat seal. While the taped lap seal is thinner than the Anaconda fold, the extra thickness of the tape makes more difficult the task of achieving a hermetic seal with the ends. Applying the tape during the tube winding operation and keeping it properly aligned adversely affect line efficiency. Furthermore, the additional expense of the additional tape member is a cost factor to be avoided.